Up-drawing continuous casting apparatus and up-drawing continuous casting method

ABSTRACT

An up-drawing continuous casting apparatus includes a holding furnace that holds molten metal, and a shape defining member that is set near a molten metal surface of a molten metal held in the holding furnace, and defines a section shape of a casting to be cast, as the molten metal passes through the shape defining member. The shape defining member is able to be switched between a joined state and a partitioned state. With such a structure, it becomes possible to form a casting having a branched structure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an up-drawing continuous casting apparatus and an up-drawing continuous casting method.

2. Description of Related Art

In Japanese Patent Application Publication No. 2012-61518 (JP 2012-61518 A), a free casting method is proposed by the inventors as an innovative up-drawing continuous casting method that does not require a mold. As described in JP 2012-61518 A, after a starter is immersed into a surface of molten metal (or a molten metal surface), the starter is drawn up, and then, the molten metal follows the starter and is also drawn out by a surface film and surface tension of the molten metal. Here, the molten metal is drawn out through a shape defining member placed near the molten metal surface, and then cooled, thereby achieving continuous casting of a casting having a desired sectional shape.

In a normal continuous casting method, a shape in a longitudinal direction is defined by a mold together with a sectional shape. In particular, in a continuous casting method, since it is necessary for solidified metal (in other words, a casting) to pass through inside of a mold, a shape of a casting that has been cast extends linearly in the longitudinal direction. On the contrary, the shape defining member in the free casting method defines only a sectional shape of a casting, and does not define a shape in the longitudinal direction. Also, since the shape defining members are able to move in a direction parallel to the molten metal surface (in other words, in a horizontal direction), a casting in various shapes in the longitudinal direction is obtained. For example, JP 2012-61518 A discloses a hollow casting (in other words, a pipe) that is formed into a non-linear shape, such as a zigzag shape or a helical shape, in the longitudinal direction.

The inventors have found out the following problem. In JP 2012-61518 A, a manufacturing method for a casting having a branched structure is not disclosed.

SUMMARY OF THE INVENTION

The present invention provides an up-drawing continuous casting apparatus and an up-drawing continuous casting method, by which a casting having a branched structure is able to be formed.

An up-drawing continuous casting apparatus according to an aspect of the present invention includes a holding furnace that holds molten metal, and a shape defining member that is set near a molten metal surface of the molten metal held by the holding furnace, and defines a sectional shape of a casting to be cast, as the molten metal passes through the shape defining member, and the shape defining member is able to be switched between a joined state and a partitioned state. With such a structure, it becomes possible to form a casting having a branched structure.

The up-drawing continuous casting apparatus may also include a molten metal cutter inserted into the molten metal that has passed through the shape defining member, in a case where the shape defining member is in the partitioned state. Further, a pair of the molten metal cutters may be arranged so as to face each other through the molten metal that has passed through the shape defining member, on a parting line on which the shape defining member is partitioned. With such a structure, it becomes possible to ensure further that a casting having a branched structure is formed.

The shape defining member includes an inner shape defining member and an outer shape defining member, and the casting to be cast may have a hollow structure.

The up-drawing continuous casting apparatus may further include a cooling part that cools and solidifies the molten metal that has passed through the shape defining member.

The up-drawing continuous casting method may be a free casting apparatus, in which, when a starter is drawn up from the molten metal surface, the molten metal follows the starter and is drawn up from the molten metal surface by a surface film and surface tension, thereby forming a retained molten metal, a shape is given to the retained molten metal by the shape defining member, and the retained molten metal is solidified from an upper side to a lower side, thereby forming a casting.

An up-drawing continuous casting method according to an aspect of the present invention includes drawing up molten metal that is held in a holding furnace, while making the molten metal pass through a shape defining member that defines a sectional shape of a casting to be cast, and solidifying the molten metal by cooling the molten metal that has been drawn up through the shape defining member, and, the shape defining member is switched from a joined state to a partitioned state during casting. With such a structure, it becomes possible to form a casting having a branched structure. The shape defining member that has been partitioned during the casting may be switched to the joined state from the partitioned state.

A molten metal cutter may be inserted into the molten metal that has passed through the shape defining member in a case where the shape defining member is in the partitioned state. Further, a pair of the molten metal cutters may be arranged so as to face each other through the molten metal that has passed through the shape defining member, on a parting line on which the shape defining member is partitioned. With such a structure, it becomes possible to further ensure that a casting having a branched structure is formed.

Also, the shape defining member may be structured by an inner shape defining member and an outer shape defining member, and cast a casting having a hollow structure may be cast.

The up-drawing continuous casting method may be a free casting method in which, when a starter is drawn up from the molten metal surface, the molten metal follows the starter and is drawn up from the molten metal surface by a surface film and surface tension, thereby forming a retained molten metal, a shape is given to the retained molten metal by the shape defining member, and the retained molten metal is solidified from an upper side to a lower side, thereby forming a casting.

According to the present invention, it is possible to provide an up-drawing continuous casting apparatus and an up-drawing continuous casting method, by which a casting having a branched structure is able to be formed.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a sectional view of a free casting apparatus according to a first embodiment;

FIG. 2A is a plan view of shape defining members 102 (when joined together), and

FIG. 2B us a plan view of the shape defining members 102 (when partitioned);

FIG. 3A is a plan view showing a positional relationship between the shape defining members 102 and molten metal cutters C1, C2 (when the shape defining members 102 are joined together), and FIG. 3B is a plan view showing a positional relationship between the shape defining members 102 and the molten metal cutters C1, C2 (when the shape defining members 102 are partitioned);

FIG. 4 is a perspective view of a casting M3 according to the first embodiment; and

FIG. 5 is a sectional perspective view taken along a cutting plane line V-V in FIG. 4.

DETAILED DESCRIPTION OF EMBODIMENTS

Herein below, a specific embodiment, to which the present invention is applied, will be explained in detail with reference to the drawings. It should be noted, however, that the present invention is not limited to the embodiment described below. Also, statements and drawings below are simplified as necessary in order to clarify the explanation.

(First Embodiment) First of all, a free casting apparatus (an up-drawing continuous casting apparatus) according to the first embodiment will be explained with reference to FIG. 1. FIG. 1 is a sectional view of the free casting apparatus according to the first embodiment. As shown in FIG. 1, the free casting apparatus according to the first embodiment includes a molten metal holding furnace 101, three inner shape defining members 102 a 1, 102 a 2, 102 a 3, an outer shape defining member 102 b, four inner cooling gas nozzles 103, support rods 104, actuators 105, and outer cooling gas nozzles 106. The xy plane in FIG. 1 structures a horizontal surface, and the z axis direction is a vertical direction. To be more specific, a positive direction on the z axis is a vertically upward direction.

The molten metal holding furnace 101 holds molten metal M1 such as aluminum and an aluminum alloy, and keeps the molten metal M1 at given temperature. In the example shown in FIG. 1, since the molten metal is not replenished in the molten metal holding furnace 101, a surface of the molten metal M1 (or a molten metal surface) is lowered along with a progress of casting. However, the molten metal may be replenished into the molten metal holding furnace 101 as necessary during casting so that the molten metal surface is kept constant. As a matter of course, the molten metal M1 may be other metal or an alloy than aluminum.

The inner shape defining members 102 a 1 102 a 2, 102 a 3 and the outer shape defining member 102 b are made of, for example, ceramics or stainless steel, and arranged near the molten metal surface. In the example in FIG. 1, three inner shape defining members 102 a 1, 102 a 2, 102 a 3 and one outer shape defining member 102 b are arranged so as to be in contact with the molten metal surface. However, the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b may be arranged so that main surfaces of the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b on the lower side (on the side of the molten metal surface) do not come into contact with the molten metal surface. To be specific, a given gap (of, for example, approximately 0.5 mm) may be provided between the main surfaces of the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b on the lower side, and the molten metal surface. The three inner shape defining members 102 a 1, 102 a 2, 102 a 3 define an inner shape of the casting M3 to be cast, and the outer shape defining member 102 b defines an outer shape of the casting M3 to be cast.

As shown in FIG. 1, the molten metal M1 follows the casting M3, is drawn up by a surface film and surface tension of the molten metal M1, and then passes through the molten metal passage portion 102 c. The molten metal, which follows the casting M3 and is drawn up from the molten metal surface by a surface film and surface tension of the molten metal, will be referred to as retained molten metal M2. An interface between the casting M3 and the retained molten metal M2 is a solidification interface.

The inner cooling gas nozzles 103 are connected to central parts of the inner shape defining members 102 a 1, 102 a 3, respectively. The inner cooling gas nozzles 103 are connected respectively to central parts of the inner shape defining member 102 a 2 that is partitioned into two. The four inner cooling gas nozzles 103 blow cooling gas (such as air, nitrogen, argon) towards the casting M3 from the central parts of the corresponding inner shape defining members 102 a 1, 102 a 2, 102 a 3, thus cooling the casting M3 from inside. At the same time, the inner cooling gas nozzles 103 support the inner shape defining members 102 a 1, 102 a 2, 102 a 3.

The two support rods 104 respectively support the outer shape defining member 102 b that is partitioned into two. A positional relation between the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b is maintained by the inner cooling gas nozzles 103 and the support rods 104. In addition, it is possible to perform a partitioning operation and a joining operation of the shape defining members 102.

The two inner cooling gas nozzles 103, and one support rod 104 are connected to each of the two actuators 105. The two actuators 105 are able to move the inner cooling gas nozzles 103 and the support rods 104 in a up-and-down direction (vertical direction) and the horizontal direction in synchronization with each other. Therefore, it is possible that the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b are moved in a downward direction as the molten metal surface is lowered along with progress of casting. Also, it is possible to move the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b in the horizontal direction. Therefore, a shape of the casting M3 in the longitudinal direction is freely changeable, and the partitioning operation or the joining operation of the shape defining members 102 is able to be performed.

The outer cooling gas nozzles (outer cooling parts) 106 are designed to blow cooling gas (such as air, nitrogen, and argon) on the casting M3 and cool the casting M3. The casting M3 is cooled by the cooling gas while the casting M3 is drawn up by a lifting device (not shown) connected to a starter ST, so the retained molten metal M2 near the solidification interface is solidified sequentially, thereby forming the casting M3.

Next, details of the shape defining members 102 will be explained with reference to FIG. 2 and FIG. 2B. FIG. 2A is a plan view of the shape defining members 102 (when joined together). FIG. 2B is a plan view of the shape defining members 102 (when partitioned). As shown in FIG. 2A and FIG. 2B, the shape defining members 102 include the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b. Sectional shapes of the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b are equivalent to sectional view taken along I-I in FIG. 2A. The xyz coordinates in FIG. 2A and FIG. 2B coincide with those in FIG. 1.

As shown in FIG. 2A, the outer shape defining member 102 b has, for example, a generally rectangular planar shape, and has a generally rectangular opening in the center. Also, as shown in FIG. 2B, the outer shape defining member 102 b is able to be partitioned in the x axis direction along a symmetry axis that is parallel to the y axis. In the example shown in FIG. 2A and FIG. 2B, each of four corners of the outer shape defining member 102 b is chamfered. Further, projecting parts, which project in the x axis direction, are provided in four corners of the opening, respectively.

As shown in FIG. 2A, each of the three inner shape defining members 102 a 1, 102 a 2, 102 a 3 has a generally rectangular planar shape, and is arrayed in the x axis direction inside the opening of the outer shape defining member 102 b. Further, as shown in FIG. 2B, the inner shape defining member 102 a 2 located in the center of the shape defining members 102 is able to be partitioned in the x axis direction along the symmetry axis that is parallel to the y axis. An interval between the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b serves as a molten metal passage portion 102 c (a hatching part) through which the molten metal passes.

As shown in FIG. 2A and FIG. 2B, the shape defining members 102 are able to be partitioned in the x axis direction along the symmetry axis (a parting line) that is parallel to the y axis. In other words, it is possible to switch the shape defining members 102 between a joined state and a partitioned state. Hence, it becomes possible to branch the casting M3 by switching the shape defining members 102 from the joined state to the partitioned state while casting. Moreover, it is possible to integrate the branched casting M3 together by switching the shape defining members 102 from the partitioned state to the joined state while casting. In other words, by using the shape defining member 102 according to this embodiment, it is possible to manufacture the casting M3 having the branched structure. Details of the casting M3 having such a branched structure will be described later.

Next, molten metal cutters for forming the branched structure in the casting M3 in collaboration with the shape defining members 102 will be explained with reference to FIG. 3A and FIG. 3B. FIG. 3A is a plan view showing a positional relation between the shape defining members 102 and the molten metal cutters C1, C2 (when the shape defining members 102 are joined together). FIG. 3B is a plan view showing a positional relation between the shape defining members 102 and the molten metal cutters C1, C2 (when the shape defining members 102 are partitioned). The xyz coordinates in FIG. 3A and FIG. 3B coincide with those in FIG. 1.

As shown in FIG. 3A and FIG. 3B, root portions of the two molten metal cutters C1, C2 extending in the y axis direction are fixed to one ends of arms A1, A2 extending in the x axis direction, respectively. The other ends of the arms A1, A2 are placed on a guide G that extends in the y axis direction, so that the other ends of the arms A1, A2 are able to slide. With such a structure, the molten metal cutters C1, C2 are able to slide in the y axis direction.

Here, the guide G is able to move on the xy plane and in the z axis direction, following the shape defining members 102. This means that the molten metal cutters C1, C2 are able to move on the xy plane and in the z axis direction, while following the shape defining members 102. The molten metal cutters C1, C2 are arranged on an upper side of the shape defining members 102, and a lower side of the solidification interface in the z axis direction. However, in order to improve dimensional accuracy of the casting M3, it is preferred that the molten metal cutters C1, C2 are provided as close to the shape defining members 102 as possible.

As shown in FIG. 3A, when the shape defining members 102 are joined together, molten metal cutters C1, C2 are arranged so as to face each other through the retained molten metal M2, which has been drawn up from the shape defining member 102, on the symmetry axis that is parallel to the y axis of the shape defining member 102. In other words, the molten metal cutters C1, C2 are not inserted into the retained molten metal M2.

Meanwhile, as shown in FIG. 3B, when the shape defining members 102 are partitioned, the molten metal cutters C1, C2 move in the Y axis direction so as to be closer to each other. Thus, separation of the retained molten metal M2 by partitioning of the shape defining members 102 is promoted. Just partitioning the shape defining members 102 may not be sufficient for separating the retained molten metal M2 as desired due to surface tension of the retained molten metal M2. Therefore, by inserting the molten metal cutters C1, C2 into the retained molten metal M2 at the same time as partitioning of the shape defining members 102, it is possible to ensure that the retained molten metal M2 is separated. Therefore, it is possible to improve dimensional accuracy of the branched structure of the casting M3.

Next, the casting M3 according to the first embodiment will be explained with reference to FIG. 4 and FIG. 5. FIG. 4 is a perspective view of the casting M3 according to the first embedment. FIG. 5 is a perspective sectional view taken along the cutting plane line V-V in FIG. 4. The casting M3 according to the first embodiment may be used for, for example, a bumper (so-called a front bumper) provided in the front of an automobile, but a usage of the casting M3 is not particularly limited. The xyz coordinates in FIG. 4 and FIG. 5 coincide with those in FIG. 1. Further, the casting M3 shown in FIG. 4 and FIG. 5 is only an example, and is not particularly limited as long as the casting M3 is a casting having a branched structure.

As shown in FIG. 4, the casting M3 according to the first embodiment includes integrated parts 201, 203, and a branched part (a branched structure) 202. The branched part 202 is provided with an opening 204 extending in the y axis direction. The opening 204 is used as, for example, a ventilating hole of a front bumper. As shown in FIG. 4, the integrated parts 201, 203 have a structure in which three angular pipes P1 to P3 arraying in the x axis direction are integrated. The integrated parts 201, 203 are formed in the joined state of the shape defining members 102 as shown in FIG. 2A and FIG. 3A.

In the branched part 202, the angular pipe P2 in the middle is partitioned in the vertical (z axis) direction, and the angular pipes P1, P2 are curved so as to be separated from each other (on opposite sides in the x axis direction). The branched part 202 is formed in the partitioned state of the shape defining members 102 as shown in FIG. 2B and FIG. 3B.

To be more specific, once the shape defining members 102 are partitioned from the joined state during casting, the casting is switched from forming of the integrated part 201 to forming of the branched part 202. At this time, a width of the partition of the shape defining members 102 is widened, and a width of the opening 204 of the branched part 202 is also widened. Therefore, an interval between the angular pipes P1, P3 is also widened. Thereafter, while the width of the partition of the shape defining members 102 is kept constant, the width of the opening 204 in the branched part 202 also becomes constant, and the angular pipes P1, P3 becomes parallel to each other. Thereafter, the width of the partition of the shape defining members 102 is reduced, and the width of the opening 204 of the branched part 202 is also reduced. Thus, the interval between the angular pipes P1, P3 is also reduced. Once the shape defining members 102 are joined together again during the casting, the casting is switched from forming of the branched part 202 to forming of the integrated part 203.

Next, a free casting method according to the first embodiment will be explained with reference to FIG. 1. First of all, the starter ST is descended, making a distal end part of the starter ST immersed in the molten metal M1 through the molten metal passage portion 102 c between the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b in the state where the shape defining members 102 are joined together. As the starter ST, it is preferred to use a starter, which has the same sectional shape as that of the integrated part 201 of the casting M3 and extends linearly in the longitudinal direction.

Next, the starter ST starts being drawn up at a given speed. At this time, even if the starter ST is separated from the molten metal surface, the retained molten metal M2 is formed, which follows the starter ST and is drawn up from the molten metal surface by the surface film and surface tension. As shown in FIG. 1, the retained molten metal M2 is formed in the molten metal passage portion 102 c between the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b. In other words, a shape is given to the retained molten metal M2 by the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b.

Next, because the starter ST is cooled by the cooling gas blown out from the inner cooling gas nozzles 103 and the outer cooling gas nozzles 106, the retained molten metal M2 is sequentially solidified from the upper side towards the lower side, and the casting M3 thus grows. This way, continuous casting of the casting M3 is achieved.

As stated so far, in the free casting method according to the first embodiment, the integrated part 201 (see FIG. 4) is first formed in the state where the shape defining members 102 are joined together (see FIG. 2A and FIG. 3A). Then, the branched part 202 (see FIG. 4) is formed in the state where the shape defining members 102 are partitioned (see FIG. 2B and FIG. 3B). Lastly, as the shape defining member 102 is joined together again (see FIG. 2A and FIG. 3A), the integrated part 203 (see FIG. 4) is formed.

The shape defining members 102 may be moved in the horizontal direction while maintaining the relative positional relation between the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b. This makes it possible to give the casting M3 various types of bent portions and curved portions, other than the branched structure.

Instead of moving the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b in the horizontal direction, the starter ST fixed to the lifting device may be moved in the horizontal direction. Alternatively, the inner shape defining members 102 a 1, 102 a 2, 102 a 3 and the outer shape defining member 102 b, and the starter ST may be moved in opposite directions in a horizontal plane.

The present invention is not limited to the foregoing embodiment, and may be changed as appropriate without departing from the gist of the invention. In particular, the casting M3 may be a solid structure instead of the hollow (pipe) structure. 

1. An up-drawing continuous casting apparatus, comprising: a holding furnace that holds molten metal; and a shape defining member that defines a sectional shape of a casting to be cast, as the molten metal passes through the shape defining member, wherein the shape defining member is set near a molten metal surface of the molten metal held by the holding furnace, and the shape defining member is able to be switched between a joined state and a partitioned state.
 2. The up-drawing continuous casting apparatus according to claim 1, further comprising: a molten metal cutter inserted into the molten metal that has passed through the shape defining member, in a case where the shape defining member is in the partitioned state.
 3. The up-drawing continuous casting apparatus according to claim 2, wherein a pair of the molten metal cutters is arranged so as to face each other through the molten metal that has passed through the shape defining member, on a parting line on which the shape defining member is partitioned.
 4. The up-drawing continuous casting apparatus according to claim 1, wherein the shape defining member includes an inner shape defining member and an outer shape defining member, and the casting to be cast has a hollow structure.
 5. The up-drawing continuous casting apparatus according to claim 1, further comprising: a cooling part that cools and solidifies the molten metal that has passed through the shape defining member.
 6. The up-drawing continuous casting apparatus according to claim 1, wherein, when a starter is drawn up from the molten metal surface, the molten metal follows the starter and is drawn up from the molten metal surface by a surface film and surface tension, thereby forming a retained molten metal, a shape is given to the retained molten metal by the shape defining member, and the retained molten metal is solidified from an upper side to a lower side, thereby forming a casting.
 7. An up-drawing continuous casting method comprising: drawing up molten metal that is held in a holding furnace, while making the molten metal pass through a shape defining member that defines a sectional shape of a casting to be cast; solidifying the molten metal by cooling the molten metal that has been drawn up through the shape defining member; and switching the shape defining member from between a joined state and a partitioned state during casting.
 8. The up-drawing continuous casting method according to claim 7, further comprising: switching the shape defining member from the partitioned state to the joined state during the casting.
 9. The up-drawing continuous casting method according to claim 7, further comprising: inserting a molten metal cutter into the molten metal that has passed through the shape defining member in a case where the shape defining member is in the partitioned state.
 10. The up-drawing continuous casting method according to claim 9, further comprising: arranging a pair of the molten metal cutters so as to face each other through the molten metal that has passed through the shape defining member, on a parting line on which the shape defining member is partitioned.
 11. The up-drawing continuous casting method according to claim 7, wherein a casting having a hollow structure is cast by the shape defining member that is structured by an inner shape defining member and an outer shape defining member.
 12. The up-drawing continuous casting method according to claim 7, wherein, when a starter is drawn up from a molten metal surface, the molten metal follows the starter and is drawn up from the molten metal surface by a surface film and surface tension, thereby forming a retained molten metal, a shape is given to the retained molten metal by the shape defining member, and the retained molten metal is solidified from an upper side to a lower side, thereby forming a casting. 